Added screen reader text to events.

css/laps.css

@@ -60,6 +60,16 @@
 #wpadminbar .laps-timeline .event-http {
   background-color: #d9534f;
 }
+#wpadminbar .laps-timeline .sr-only {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  margin: -1px;
+  padding: 0;
+  overflow: hidden;
+  clip: rect(0, 0, 0, 0);
+  border: 0;
+}
 #wpadminbar .tooltip {
   position: absolute;
   z-index: 100000;